Copenhagen, 2012-10-23 14:06 CEST (GLOBE NEWSWIRE) -- Merck initiated the trial in 2011 to evaluate the efficacy and safety of grass AIT versus placebo in the treatment of grass pollen induced allergic rhinoconjunctivitis (hay fever). The primary endpoint was the combined rhinoconjunctivitis daily symptom score (DSS) and rhinoconjunctivitis daily medication score (DMS) during the grass pollen season. The trial, which included approximately 1,500 patients, is the largest study of grass AIT to date.